Why did they kill John and Robert Kennedy?

[gyroscope]

the establishment and the powers that be (including the rightwing of both parties, the MIC, Wall Street banks, etc) could not tolerate another populist FDR-like president who would stand up to them.

as General Smedley Butler testified they already attempted a coup of FDR at least once while he was in office but failed. Kennedy also rejected the DoD's proposal to blow up US airliners and make it look like Castro was responsible (see Operation Northwoods). he was not anyone's puppet, so one way or another they had to get rid of him. had they lived John Kennedy and his brother would have represented another 16 years (2 terms each) of FDR-style populist leadership in the US. and there was no way in hell they would allow that to happen and this time they would not fail in their coup.